1 / 26

260 likes | 468 Vues

Geometry Textures. Rodrigo de Toledo, ( PhD candidate at LORIA-INRIA) (Researcher at Tecgraf, PUC-Rio) Bin Wang and Bruno Levy. Geometry Textures. Geometry Texture is a patch of surface A set of GT is used to represent/render an entire object Representation is based on height maps

Télécharger la présentation
## Geometry Textures

**An Image/Link below is provided (as is) to download presentation**
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.
Content is provided to you AS IS for your information and personal use only.
Download presentation by click this link.
While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

**Geometry Textures**Rodrigo de Toledo,(PhD candidate at LORIA-INRIA) (Researcher at Tecgraf, PUC-Rio) Bin Wang and Bruno Levy**Geometry Textures**• Geometry Texture is a patch of surface • A set of GT is used to represent/render an entire object • Representation is based on height maps • Rendering is based on GPU ray casting**Motivation**• In highly detailed meshes, small triangles represent mesostructures • Maybe it is better to render these mesostructres using a more appropriate representation • Main idea: to use mesoscale rendering algorithms for macroscale visualization**Summary**• Motivation • Scale level classification • Mesoscale • GPU ray-casting of height maps • Conversion • Visualizing • Results**Macroscale**Scene-scale Microscale Mesoscale Visualization algorithmsgrouped into scale levels • z-buffer • ray tracing • spatial subdivision • culling • (between macro and micro) • textures • mesostructures • object representation • shading • LOD • impostors • complex lighting models • photon mapping • BSSRDF**Mesoscale**• Mesostructure representation • Color map • Normal map (bump) • Height map • Volumetric mesostructure • Shading function (BRDF)**Mesostructure visualization**Mesoscale Mesoscalemethods • Expected rendering effects**Summary**• Motivation • Scale level classification • Mesoscale • GPU ray-casting of height maps • Conversion • Visualizing • Results**Linear search**Binary search BinRayCasting() { for 1..M { Δ Δ / 2 Δ z(P) ? -Δ : Δ P P + Δ’ } } ray path sampled N times missing a sample if is big v P0 P1 second searching step P2 Pi-1 Pi-1 P'i Pi Pi hm(x,y) Height-map GPU ray casting**Height-map GPU ray casting**• Silhouette, self-occlusion and self-shadow • Balance between steps 66 85 70 55 Top viewBalance: more speed Profile view Balance: more quality [Policarpo and Oliveira 2005]**Height-map GPU ray casting**It can be used to mesoscale visualization But, we propose to use it for macroscale visualization: Geometry Textures**Geometry Textures**• Parallel hexahedron with height map in its interior • Each one has its own orientation • HM domain is not restricted to a perfect rectangle • Previous work on multiple height maps: • Relief Texture Mapping [OB00] • Rendering Geometry with Relief Texture [BD06] • Real-time VDM using per-pixel visibility [PDG05]**Summary**• Motivation • Scale level classification • Mesoscale • GPU ray-casting of height maps • Conversion • Visualizing • Results**Verifyfolding**Conversion overview Mesh Partioning Bounding-box Maps extraction mesh x, y definition (PCA analysis) color,normal,height maps extraction Partioning Overlapping bbox domain in 3D maps dilation z definition (normal median) Geometry Texture set**Partitioning**• The most complex step in conversion • Each part should not present any folding (no overhang) • Domain as square as possible**Partitioning strategies**VSA [Steiner et al. 04] PGP [Ray et al. 05]**Summary**• Motivation • Scale level classification • Mesoscale • GPU ray-casting of height maps • Conversion • Visualizing • Results**Geometry Texture Results**Using dragon example to test: (1.2 million triangles) • Rendering quality • Rendering speed • Pre-processing performance • Memory space**mesh**5122 2562 1282 Geometry Texture Results(rendering quality) mesh 5122 2562 1282 2562 is the best option**Geometry Texture Results(rendering quality)**Seamless reconstruction due to overlapping + z-buffer • GT should respect z-buffer rules: • Compute depth + test + update z-buffer • Z-fight (for the same color)**Geometry Texture Results(rendering performance)**• 2562 GeoTex is faster than mesh for screen-size smaller than 800x600 GeForce 8800**Geometry Texture Results(pre-processing and memory)**• Original Dragon: 13.3 MB • From quality point of view: 2562 is good • If memory is a problem: 1282**Conclusion**• Positive aspects: • Rendering speed follows a LOD behavior. • It can be used with other polygonal objects in scene (z-buffer). • Memory reduction is possible without losing too much information. • Drawbacks: • Too much complex conversion algorithm. • Especially the partitioning step (which is considerably elaborate). • We suggest the use of multilayer height maps (FW). • It is hard to battle VBO speed in recent graphics cards. • We should test GT with more complex models (such as David). • If multiple models on the screen at the same time, GT can battle VBO. [PDG05]**Future work**• Image operations on geometry textures • Multilayer height maps • Sequence of height maps for the entire object • Layers forming a CSG representation**Thank you**Questions?

More Related